INTERFERENCE EFFECTS IN (E,2E)-DIFFERENTIAL CROSS-SECTIONS IN DOUBLY SYMMETRICAL GEOMETRY

This work investigates theoretically the triply differential cross sections for electron-impact ionization of He in doubly symmetric geometry, i.e. equal energies and equal emission angles for the two electrons in the final state. Dominant ionization mechanisms are identified and the contribution of different scattering amplitudes are discussed. It turns out that the cross section in doubly symmetric geometry is strongly influenced by interference of these amplitudes. In particular, the theory predicts zero cross sections due to interference under certain kinematical conditions. This explains the appearance of deep minima in the measured differential cross sections.